The operation of diesel and spark ignition internal combustion engines is typically accompanied by the formation of sludge, lacquer and resinous deposits which adhere to the moving engine parts and thereby reduce engine efficiency. In order to prevent or reduce the formation of these deposits, a wide variety of chemical additives have been developed for incorporation into lubricating oils. These additives are commonly referred to as detergents and dispersants. Dispersants have the ability to keep deposit forming materials suspended in the oil so as to retard deposit formation during engine operation. Detergents have the ability to remove pre-existing deposits from the engine during engine operation and to neutralize acids in railroad, marine and automotive engines.
A large number of railroad and tugboat diesel engines use silver-plated bearings. As a result, the lubricating oil requires acceptable silver wear control and corrosion performance in addition to deposit control and alkalinity. Mannich bases and their salts have been known to be effective to protect silver bearing parts in such engines without the disadvantages associated with the use of chlorinated and dithiophosphate additives.
Mannich bases and their salts are also known to be particularly useful in lubricating oils, fuels, greases and plastics as antioxidants. Hydrocarbon materials are highly susceptible to chemical action on aging, exposure to sunlight and in their normal use. Such oxidation can lead to the deposit of undesirable residues in lubricants, fuels and greases and to discoloration of plastics.
Frequently, the inclusion of additives in lubricating oils and fuels to control deposits, wear and oxidation cause compatibility problems. In addition, it is uneconomical to add many additives in order to achieve all these functions.
Thus, there is a great need for the development of a single multifunctional agent that will perform all these desired functions.
One class of lubricating oil additives typically used as dispersants, detergents, oxidation inhibitors and anti-wear additives are Mannich condensation products of an alkylphenol, an aldehyde and an amine.
Various Mannich condensation products known in the prior art as lubricating oil additives are metal salts. Currently, there is no carbonation process in the prior art for making Group II metal carbonated, overbased Mannich condensation products of alkylphenol which have a high alkalinity reserve for neutralizing acids in engines and at the same time have acceptable viscosity. It is believed that the carbonate, overbased Mannich condensation products of alkylphenols of the present invention are superior to the prior art salts of Mannich condensation products of alkylphenols for providing the functions of detergent-dispersants, anti-wear and oxidation agents in one additive because of their greater alkalinity reserve and acceptable viscosities.
The ability of additive compositions to neutralize acids in engines can be measured by determining the total base number (TBN) or the alkalinity reserve of the composition. Higher TBNs reflect a greater capacity for these compositions to neutralize acids generated during engine operation. However, the TBN of a composition is directly related to the amount of diluent oil present. Thus, more concentrated compositions will have a higher TBN than those containing more diluent.
The preparation of Group II metal salts of Mannich condensation products of alkylphenol compositions is well known in the art. A number of patents have discussed processes for making Group II metal salts of the Mannich condensation products of alkylphenols, but none have included a carbonation step in the process.
For example, U.S. Pat. No. 3,036,003 discloses a process for making a metal salt of a condensation product of an alkylene polyamine, an aldehyde and substituted phenol.
U.S. Pat. No. 3,340,190 discloses the preparation of a mixture of the exactly neutralized calcium salt of N,N′-bis(alkyl substituted hydroxybenzyl)alkylene diamine and a bis (alkenylsuccinimide) of polyalkylene polyamine or of a urea condensation derivative of polyalkylene polyamine, N,N′-bis(polyazalkylamino) ureylene.
U.S. Pat. No. 3,586,629 discloses the preparation of salts obtained by reacting the condensation product of an alkyl hydroxy aromatic compound, an aldehyde and an amine or alkali metal salt thereof with a metal base. These salts provide excellent detergency characteristics to an organic industrial fluid.
U.S. Pat. No. 3,798,163 teaches a method for inhibiting exhaust valve recession in natural gas fueled internal combustion engines with the use of composition comprising a lubricating oil, a metal sulfonate and at least one metal salt of a condensation product of an alkylene polyamine, an aldehyde and a substituted phenol.
U.S. Pat. No. 3,958,624 discloses an improved anti-fouling additive for use in organic heat transfer fluids comprising a combination of a barium overbased calcium sulfonate and a phenolic antioxidant, an alkaline earth aminophenate.
U.S. Pat. No. 4,025,316 discloses the preparation of polymeric alkyl-hydroxy benzyl N-substituted amines having a high degree of ring formation derived from the condensation reaction of C8-C40 aliphatic alkyl substituted hydroxy aromatic, an aldehyde and an amine.
U.S. Pat. No. 4,088,586 discloses the preparation of salts of Mannich bases from tetrapropenylphenol, formaldehyde and diethylenetriamine when the molar ratio of the reactant is 1 mole tertapropenylphenol to 0.5 to 0.85 mole formaldehyde to at least 0.3 mole of diethylenetriamine having outstanding viscosity and alkalinity value properties.
U.S. Pat. No. 4,140,492 discloses the preparation of borated derivatives of oil-soluble Mannich bases for use in combination with coadditive hydrocarbons for flow improvers for middle distillate fuel oils.
U.S. Pat. No. 4,157,308 discloses the preparation of Mannich base compositions and their metal salts from phenolic mixtures consisting of phenol alkylated with a propylene tetramer and phenol alkylated with a straight-chain alpha-olefin.
U.S. Pat. No. 4,231,759 discloses a liquid hydrocarbon combustion fuel containing an additive composition comprising the Mannich condensation product of a high molecular weight alkyl-substituted hydroxyaromatic compound wherein the alkyl group has a molecular weight of from about 600 to about 3,000.
U.S. Pat. No. 4,655,949 discloses novel lubricating oil composition comprising an organomettalic additive containing a metal selected from Groups I, Ib and VIII chelated with the reaction product of formaldehyde, an amino acid and a phenol.
U.S. Pat. Nos. 4,734,211; 4,764,296 and 4,820,432 disclose a lubricating oil composition for railway diesel engines which contains calcium salt of Mannich reaction product among other additives. The Mannich base is prepared using an alkyl substituted hydroxy aromatic compound, specifically para-alkyl phenol. The TBN of the product was approximately 160.
Typically, Mannich bases are prepared by reacting an alkylphenol with an aldehyde and an amine wherein the amine is a primary or secondary aliphatic or aromatic amine or polyamine, and the aldehyde is an aliphatic or aromatic aldehyde. The alkyl group of the phenol can be straight-chain or branched-chain. Optionally, a promoter may be used during the condensation reaction.
The prior art process for making the metal salt of the Mannich bases is typically by the addition of a metal oxide, hydroxide or hydroperoxide. Optionally, ethylene glycol is added to the reaction mixture to promote the salt formation.